Recently, multicarrier transmissions utilizing CDTD (Cyclic Delay Transmit Diversity) have been proposed in which a multicarrier-signal transmitting apparatus including multiple transmission antennas adds different cyclic delays to transmission signals to be simultaneously transmitted from the transmission antennas (see Non-patent Document 1). When CDTD is used, the channel frequency selectivity always increases, thereby preventing the reception power from decreasing over the entire frequency of a reception channel, and achieving excellent average BER (Bit Error Rate) characteristics in a receiving apparatus.
FIG. 11 shows a case where a signal is transmitted from transmission antennas 1a and 1b included in a multicarrier-signal transmitting apparatus to a reception antenna 2a included in a multicarrier-signal receiving apparatus. As shown in FIG. 11, signals s1 and s2 are respectively transmitted from the transmission antennas 1a and 1b, and a multiplexed wave thereof is received by the reception antenna 2a. The multicarrier-signal transmitting apparatus utilizing CDTD adds different cyclic delays to the signals s1 and s2 to be respectively transmitted from the transmission antennas 1a and 1b. 
FIG. 12 shows the configuration and the power of the reception signal.
FIG. 12 (a) shows an example state of subcarriers and OFDM symbols being respectively arranged along the horizontal and the vertical axes representing frequency and time. As shown in FIG. 12, channel estimation symbols P1 to P5 are arranged at every 6 subcarriers.
FIG. 12 (b) shows a state of the reception signal being distorted in the frequency domains with respect to the power where the vertical and the horizontal axes represent frequency and power. When a transmission apparatus uses CDTD, the frequency selectivity increases as shown in FIG. 12 (b). Therefore, enhancement of the reception characteristics can be expected.
Non-patent Document 1: IEICE technical report RCS2004-392, “Application of Cyclic Delay Transmit Diversity to DS-CDMA using Frequency-domain Equalization”, issued on March, 2005 by the Institute of Electronics, Information and Communication Engineers.